title: Quadrupole effects in tetragonal crystals PrCu₂Si₂ and DyCu₂Si₂.
abstract: We have investigated quadrupole effects in tetragonal crystals of PrCu2Si2 and DyCu2Si2 by means of low-temperature ultrasonic measurements. The elastic constant C44 of PrCu2Si2 exhibits pronounced softening below 70 K down to a Néel temperature TN = 20 K, which is described in terms of a quadrupole susceptibility for a Γ5 doublet ground state and a Γ3 singlet first excited state located at 15.6 K in the crystalline electric field scheme. The C44 and C66 of DyCu2Si2 also show softening below 70 K down to TN1 = 9.7 K. A low-lying pseudo-sextet state consisting of three Kramers doublets of Γ6⊕2Γ7 brings about softening of C44 and C66 in DyCu2Si2.
authors.affiliation: Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan. mitsumoto@phys.sc.niigata-u.ac.jp
authors.forename: Keisuke
authors.initials: K
authors.lastname: Mitsumoto
authors.forename: Saori
authors.initials: S
authors.lastname: Goto
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Nemoto
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Akatsu
authors.forename: Terutaka
authors.initials: T
authors.lastname: Goto
authors.forename: Nguyen D
authors.initials: ND
authors.lastname: Dung
authors.forename: Tatsuma D
authors.initials: TD
authors.lastname: Matsuda
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Haga
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Kiyohiro
authors.initials: K
authors.lastname: Sugiyama
authors.forename: Rikio
authors.initials: R
authors.lastname: Settai
authors.forename: Yoshichika
authors.initials: Y
authors.lastname: Onuki
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D003460:Crystallization; D004419:Dysprosium / Q000737:chemistry*; D008956:Models, Chemical; D011221:Praseodymium / Q000737:chemistry*; D011789:Quantum Theory; D012825:Silicon / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D004419:Dysprosium; D003300:Copper; D011221:Praseodymium; D012825:Silicon